/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jasper.tagplugins.jstl.core;

import org.apache.jasper.compiler.tagplugin.TagPlugin;
import org.apache.jasper.compiler.tagplugin.TagPluginContext;

public class Param implements TagPlugin {

	public void doTag(TagPluginContext ctxt) {

		// don't support the body content

		// define names of all the temp variables
		String nameName = ctxt.getTemporaryVariableName();
		String valueName = ctxt.getTemporaryVariableName();
		String urlName = ctxt.getTemporaryVariableName();
		String encName = ctxt.getTemporaryVariableName();
		String index = ctxt.getTemporaryVariableName();

		// if the param tag has no parents, throw a exception
		TagPluginContext parent = ctxt.getParentContext();
		if (parent == null) {
			ctxt
					.generateJavaSource(" throw new JspTagExcption"
							+ "(\"&lt;param&gt; outside &lt;import&gt; or &lt;urlEncode&gt;\");");
			return;
		}

		// get the url string before adding this param
		ctxt.generateJavaSource("String " + urlName + " = "
				+ "(String)pageContext.getAttribute(\"url_without_param\");");

		// get the value of "name"
		ctxt.generateJavaSource("String " + nameName + " = ");
		ctxt.generateAttribute("name");
		ctxt.generateJavaSource(";");

		// if the "name" is null then do nothing.
		// else add such string "name=value" to the url.
		// and the url should be encoded
		ctxt.generateJavaSource("if(" + nameName + " != null && !" + nameName
				+ ".equals(\"\")){");
		ctxt.generateJavaSource("    String " + valueName + " = ");
		ctxt.generateAttribute("value");
		ctxt.generateJavaSource(";");
		ctxt.generateJavaSource("    if(" + valueName + " == null) "
				+ valueName + " = \"\";");
		ctxt.generateJavaSource("    String " + encName
				+ " = pageContext.getResponse().getCharacterEncoding();");
		ctxt.generateJavaSource("    " + nameName
				+ " = java.net.URLEncoder.encode(" + nameName + ", " + encName
				+ ");");
		ctxt.generateJavaSource("    " + valueName
				+ " = java.net.URLEncoder.encode(" + valueName + ", " + encName
				+ ");");
		ctxt.generateJavaSource("    int " + index + ";");
		ctxt.generateJavaSource("    " + index + " = " + urlName
				+ ".indexOf(\'?\');");
		// if the current param is the first one, add a "?" ahead of it
		// else add a "&" ahead of it
		ctxt.generateJavaSource("    if(" + index + " == -1){");
		ctxt.generateJavaSource("        " + urlName + " = " + urlName
				+ " + \"?\" + " + nameName + " + \"=\" + " + valueName + ";");
		ctxt.generateJavaSource("    }else{");
		ctxt.generateJavaSource("        " + urlName + " = " + urlName
				+ " + \"&\" + " + nameName + " + \"=\" + " + valueName + ";");
		ctxt.generateJavaSource("    }");
		ctxt
				.generateJavaSource("    pageContext.setAttribute(\"url_without_param\","
						+ urlName + ");");
		ctxt.generateJavaSource("}");
	}
}
